Most laser cutting machines of the gantry type utilize bellows type covers for protecting the mechanism that supports and drives the laser cutting head carriage. One such system is disclosed in U.S. Pat. No. 5,854,460. However, the use of such bellows type cover for enclosing a laser beam guide tends to have detrimental effects on the accuracy of the laser beam. This is due to the fact that such bellows type cover in essence acts the same as an accordion so that, when the laser head carriage moves, some portions of the cover would compress while other portions of it would expand. And when that happens, a vacuum is created inside the beam guide so that dirt and dust tend to be sucked into the beam guide. Such dirt and dust then create a disturbance to the laser beam, and therefore affect its accuracy.
To overcome such shortcomings, a new type of beam guide that allows the laser cutting head to freely move and yet at the same time not create any vacuum is needed.